As the era of high oil prices has arrived, the importance of plant biomass is being magnified as a source of bioenergy. A first generation biofuel production using a saccharification process of starch which is present in crops has caused a rise in agricultural commodity prices, food shortages, and a financial crisis, and thus the development of the related art is being eschewed. Whereas a study on a second generation biofuel production using lignocellulosic cellulose which is present in silver grass, switch grass, and poplar, which are inedible biomass crops, is vigorously in progress. However, the efforts to increase and continuously maintain plant biomass production may be required basically to produce a large amount of energy enough to substantially substitute for a fossil fuel. Accordingly, a study on the development of vascular tissues including a cambium which mainly affect a secondary growth and the growth control mechanism is required.
The vascular tissues of plants, as a moving path of materials which are necessary for the growth and development of plants including water and nutrients, have a distinguishing structure formed by each of the cells having a specific function. In an elongation, which is a primary growth, the vascular tissues of the stem are generated by an apical meristem which is present at the uppermost part, and include a procambium, primary phloem, and xylem. Cambium cells expanded in a fibrovascular tissue between the bundles for the secondary growth are formed over time, secondary phloem and xylem are developed in an opposite direction from the cambium cells as an initial cell, and thereby a closed ring-shaped structure is formed.
Various plant growth hormones become involved in the development of vascular tissues of the stem. Auxin and cytokinin which are closely related to the activity of overall meristematic tissues affect cell division of the cambium, and gibberellin and ethylene also become involved in activity of the cambium. Further, brassinosteroid controls the number or pattern of the vascular bundle, which is determined according to the auxin maxima generated by controlling the movement of auxin. In addition, specific genes are known for becoming involved in each tissue-specific formation. For example, ATHB8, CNA(ATHB15), PHB, PHV, and REV which belong to a HD-ZIP III gene group are all mainly expressed in the cambium of vascular tissues, and development directions of phloem and xylem, and differentiation of xylem are known to be controlled by the above-described genes in each of the vascular bundles. Further, KANADI which is another control factor controls expression of the above-described HD-ZIP III through miRNA165/166, and this is reported to control a formation of vascular tissues through interaction with auxin.
Although a study on this complex mutual control action is well performed, a case of changing an amount of biomass which may be actually produced through a modification of the related gene has not been reported. This means that a factor becoming involved in the development of the specific tissues has a limitation in increasing an amount of production of biomass.
However, Arabidopsis thaliana has a short first generation period of about 6 weeks from germination to the formation of the next seed, and mutants of Arabidopsis thaliana having various forms may be simply made using chemical materials. Further, the size of Arabidopsis thaliana is small enough to be raised in a glass container, and the size of the genome is small. Accordingly, Arabidopsis thaliana is a popular model organism in the study of plants. A plant height is about 30 cm, a flower bud is formed about 3 weeks after germination under long-day conditions, the first seed may be obtained in 5 to 6 weeks, and self-fertilization is possible as well as artificial crossing. The most noticeable characteristic is that Arabidopsis thaliana is a plant having the smallest genomic size in phanerogamous plants, the size of the genome is known to be 1×108 base pairs/haploid. The chromosome number is 2n=10, and a repeated sequence is small, either. A genetic map of which a title is restriction fragment length polymorphism (RELP) was completed by Howard Goodman, etc. of Massachusetts Institute of Technology (MIT), and a dielectric plan of “the Arabidopsis thaliana edition” was launched from 1990 under the aegis of the National Science Foundation (NSF). Accordingly, the present inventors attempted to find a new gene to increase the biomass production using Arabidopsis thaliana which has the above-described advantages.